Thanks @obfusk, we'd better do some testing first but that sounds good.

OK I got around to testing obfusk's patch, something still needs patching:
TEST SETUP AS FOLLOWS:

Python 3.8 buildozer test with obfusk's patches:
buildozer.spec: (relevant lines for testing helloworld from kivy site)

requirements = python3==3.8.6,hostpython3==3.8.6,kivy==2.0.0rc4,https://github.com/kivymd/KivyMD/archive/master.zip,pygments,sdl2_ttf==2.0.15
#obfusk's patches
p4a.source_dir = %(source.dir)s/../python-for-android

RESULTS from logcat on Pixel 4 XL: (PASS)
http://sunsaturn.com/kivy/3.8.txt

Python 3.9 buildozer test with obfusk's patches:
buildozer.spec: (relevant lines for testing helloworld from kivy site)

requirements = python3==3.9.0,hostpython3==3.9.0,kivy==2.0.0rc4,https://github.com/kivymd/KivyMD/archive/master.zip,pygments,sdl2_ttf==2.0.15
#obfusk's patches
p4a.source_dir = %(source.dir)s/../python-for-android

RESULTS from logcat on Pixel 4 XL: (FAIL)
http://sunsaturn.com/kivy/3.9.txt

Additional comments: only thing that affects it failing is (python3==3.9.0,hostpython3==3.9.0) after running numerous tests with different modules like kivymd or just setting python3==3.9.0,hostpython3==3.9.0,kivy==2.0.0rc4 only in requirements line.
As you can see from logs, kivy is not getting loaded for some reason

@syleishere that is a bug in kivy.

Also: it would have been easier to diagnose that if you had also provided build logs 😄

With the proposed kivy patch, a simple "hello world" p4a kivy app seems to work fine now.

• fixed merge conflict after changes to develop
• updated Python to 3.9.1 (since that has been working fine for me)

Updated to python 3.9.2 (which has been working fine for me, but AFAIK still requires master for kivy apps).

If updating to 3.9 is still not desirable yet, may I suggest at least updating to 3.8.8 to get the latest (security) fixes?

I'd be happy to make a PR for that. I haven't tested it myself though, since I've been using 3.9.2.

Yes please go ahead with the security fixes patch version

Yes please go ahead with the security fixes patch version

See #2451.

Closing as #2586 introduced Python 3.9.9, which is newer than the version proposed in this PR.